In this letter, we propose a novel packet detection and symbol timing synchronization algorithm for MB-OFDM UWB system over multi-path channel. To find more reliable and exact symbol timing, we utilize the merits of the auto- and cross-correlation at the same time. The auto-correlator can gather the energy of the received signal which is distorted by multipath fading. And, the cross-correlator can estimate symbol timing to sample level precision. We define the detection and symbol timing metric as the moving sum of autocorrelation of the pre-computed cross-correlated signals over zero pad duration. Simulation results show that the proposed algorithm can detect the presence of a signal with less than -4 dB SNR and find DFT window with at most 0.1 dB SNR reduction upon the receipt of two symbols.

A new estimation algorithm of clock drift in symbol duration for high precision ranging, based on multiple symbols of chirp spread spectrum (CSS) is proposed. Since the permissible error of a crystal oscillator in CSS is relatively high given the need to lower device costs, ranging results are perturbed by clock drift. We establish the phenomenon of clock drift in multiple symbols of CSS, and estimate the clock drift in symbol duration based on phase difference between adjacent symbols. The proposed algorithm is analyzed, and verified by Monte Carlo simulations.

In this letter, we suggest two new efficient hardware structures of correlators for packet and frame synchronization of MB-OFDM UWB. In the proposed structure 1, we suggest a hierarchical structure composed of 8 and 16 tap sub-correlators instead of ordinary 128 tap correlators. In the proposed structure 2, we suggest a structure which uses quantized coefficients and simplified multipliers. Results of simulations indicates that the hardware complexities of proposed structures are reduced to about 54% and 31% with minor performance loss, compared with a conventional method.

In this paper, we propose a new code set which has very low spectral peak to average ratio (SPAR) and good correlation properties for DS-UWB. The codes which have low SPAR are suitable for DS-UWB system which operates in UWB (3.110.4 GHz) because they can utilize more power than high SPAR codes can do. And, in order to reduce inter symbol interference (ISI) and inter piconet interferences, the codes which have good auto- and cross-correlation properties must be used. In this paper, we propose three items; (1) a new code generation method which can generate good SPAR and auto-correlation codes, (2) code selection criteria, and (3) a code set, which has been selected according to the proposed selection criteria. The proposed code set has SPAR reduced about 0.22 dB and GMF improved by 30% compared to the previous code set while it is maintaining almost same cross-correlation properties. Each code of the proposed code set, therefore, has gained 1.43 dB SIR on an average compared to that of the previous code set.